As a conventional balanced/unbalanced converter, for instance a balanced/unbalanced converter described in Patent Literature 1 (Japanese Unexamined Patent Publication No. 2000-188218) is known. The conventional balanced/unbalanced converter described in Patent Literature 1 includes a first strip line, a second strip line, a third strip line that is electromagnetically coupled with the first strip line, and a fourth strip line that is electromagnetically coupled with the second strip line. One end of the first strip line is electrically connected to an unbalanced terminal, and the other end of the first strip line is electrically connected to one end of the second strip line. The other end of the second strip line is open.